ISO 15031-6:2005

INTERNATIONAL ISO
STANDARD 15031-6
First edition
2005-12-01


Road vehicles — Communication
between vehicle and external equipment
for emissions-related diagnostics —
Part 6:
Diagnostic trouble code definitions
Véhicules routiers — Communications entre un véhicule et un
équipement externe pour le diagnostic relatif aux émissions —
Partie 6: Définition des codes d'anomalie de diagnostic




Reference number
ISO 15031-6:2005(E)
©
ISO 2005

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ISO 15031-6:2005(E)
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ISO 15031-6:2005(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 1
4 General specifications. 6
5 Format structure . 7
5.1 Description . 7
5.2 ISO/SAE controlled codes (core DTCs). 8
5.3 Manufacturer controlled codes (non-uniform DTCs). 8
5.4 Body system groupings (DTC numbers and descriptions are given in Annex C). 8
5.5 Chassis system groupings (DTC numbers and descriptions are given in Annex C) . 8
5.6 Powertrain system groupings (DTC numbers and descriptions are given in Annex B) . 9
5.7 Network groupings (DTC numbers and descriptions are given in Annex C) . 9
6 Diagnostic trouble code descriptions . 9
6.1 Diagnostic trouble code application. 9
6.2 Powertrain systems. 9
6.3 Body systems. 10
6.4 Chassis systems. 10
6.5 Network and vehicle integration systems. 10
7 Change requests. 11
Annex A (normative) Diagnostic trouble code naming guidelines . 12
Annex B (normative) Powertrain system diagnostic trouble codes . 15
Annex C (normative) Network communication system, body system, and chassis system
groupings . 90
Annex D (normative) DTC Failure Category and Subtype definition . 118

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ISO 15031-6:2005(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 15031-6 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 3,
Electrical and electronic equipment.
ISO 15031 consists of the following parts, under the general title Road vehicles — Communication between
vehicle and external equipment for emissions-related diagnostics:
⎯ Part 1: General information
⎯ Part 2: Terms, definitions, abbreviations and acronyms
⎯ Part 3: Diagnostic connector and related electrical circuits, specification and use
⎯ Part 4: External test equipment
⎯ Part 5: Emissions-related diagnostic services
⎯ Part 6: Diagnostic trouble code definitions
⎯ Part 7: Data link security

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ISO 15031-6:2005(E)
Introduction
ISO 15031 consists of a number of parts which taken together provide a coherent self-consistent set of
specifications to facilitate emissions-related diagnostics. Parts 2 through 7 are based on SAE-recommended
practices.
This part of ISO 15031 is based on SAE J2012: MAR99 (Recommended Practice for Diagnostic Trouble Code
Definitions).
ISO 15031-1 provides an introduction to the series of International Standards.
Most automobile manufacturers equip at least a portion of their product line with some on-board diagnostic
(OBD) capability. These systems provide an indication as to the general location of the diagnosed malfunction.
This information is provided through an alphanumeric code.

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INTERNATIONAL STANDARD ISO 15031-6:2005(E)

Road vehicles — Communication between vehicle and external
equipment for emissions-related diagnostics —
Part 6:
Diagnostic trouble code definitions
1 Scope
This part of ISO 15031 provides recommended uniformity for alphanumeric trouble codes. It further provides
guidance for uniform messages associated with these codes.
It specifies several sections addressing format, structure, messages and a few examples, and is applicable to
electrical/electronic systems diagnostics of motor vehicles.
Annex A specifies the diagnostic trouble code naming guidelines for signals from components, signals to
components, system based diagnostics, and signals using a subfault strategy.
Annex B specifies the actual code assignments and description for powertrain system diagnostic trouble
codes.
Annex C specifies the actual code assignments and description for network communication system diagnostic
trouble codes, body system diagnostic trouble codes, and chassis system diagnostic trouble codes.
Annex D specifies the DTC failure category and Subtype definition of the DTC failure type byte which is an
extension of a base DTC to more precisely describe the fault symptom of the DTC.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO/TR 15031-2, Road vehicles — Communication between vehicle and external equipment for emissions-
related diagnostics — Part 2: Terms, definitions, abbreviations and acronyms
ISO 14229-1, Road vehicles — Unified diagnostic services (UDS) — Part 1: Specification and requirements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 15031-2 and the following apply.
3.1
circuit/open
fixed value or no response from the system where specific high or low detection is not feasible or can be used
in conjunction with circuit low and high codes where all three circuit conditions can be detected
NOTE The term “malfunction” has, in most cases, been deleted from the DTC description.
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ISO 15031-6:2005(E)
3.2
range/performance
circuit in the normal operating range, but not correct for current operating conditions
NOTE This may be used to indicate stuck or skewed values indicating poor performance of a circuit, component or
system.
3.3
low input
circuit voltage, frequency, or other characteristic measured at the control module input terminal or pin that is
below the normal operating range
3.4
high input
circuit voltage, frequency, or other characteristic measured at the control module input terminal or pin that is
above the normal operating range
3.5
bank
specific group of cylinders sharing a common control sensor
NOTE 1 Bank 1 always contains cylinder number 1; bank 2 is the opposite bank.
NOTE 2 If there is only one bank, bank 1 DTCs are used, and the word “bank” may be omitted. With a single bank
system using multiple sensors, bank 1 is used.
3.6
sensor location
location of a sensor in relation to the engine air flow, starting from the fresh air intake through to the vehicle
tailpipe or fuel flow from the fuel tank to the engine, numbered in order 1, 2, 3 and so on
NOTE See Figure 1 through Figure 7.

Key
B1 cylinder Bank 1 S1 sensor 1 1 V6/V8/V12 cylinder engine with exhaust banks
B2 cylinder Bank 2 S2 sensor 2 2 catalyst
 S3 sensor 3 3 tail pipe
a
wide range
b
heated
Figure 1 — Example of V6/V8/V12 cylinder engine with two exhaust banks and four catalysts
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ISO 15031-6:2005(E)

Key
B1 cylinder Bank 1 S1 sensor 1 1 V6/V8/V12 cylinder engine with exhaust banks
B2 cylinder Bank 2 S2 sensor 2 2 catalyst
 S3 sensor 3 3 tail pipe
a
wide range
b
heated
Figure 2 — Example of V6/V8/V12 cylinder engine with two exhaust banks and three catalysts

Key
B1 cylinder Bank 1 S1 sensor 1 1 4-cylinder engine with exhaust banks
 S2 sensor 2 2 catalyst
 S3 sensor 3 3 tail pipe
a
wide range
b
heated
Figure 3 — Example of L4/L5/L6 cylinder engine with one exhaust bank and two catalysts
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ISO 15031-6:2005(E)

Key
B1 cylinder Bank 1 S1 sensor 1 1 4-cylinder engine with exhaust banks
 S2 sensor 2 2 catalyst
  3 tail pipe
a
wide range
b
heated
Figure 4 — Example of L4/L5/L6 cylinder engine with one exhaust bank and one catalyst
Intake air system pressure sensor location for boosted applications in relation to the engine air flow, including
the fresh air inlet, boost device and engine manifold.

Components
A air cleaner
B MAF
C throttle body
D turbocharger/supercharger
E MAP (manifold pressure closest to the intake valves)
F inlet (pressure after the throttle body, but before the pressurizing device)
G BARO (atmospheric pressure)
Figure 5 — Turbocharger/supercharger pressure sensor location draw-thru system
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ISO 15031-6:2005(E)

Components
A air cleaner
B MAF
C throttle body
D turbocharger/supercharger
E MAP (manifold pressure closest to the intake valves)
F boost (pressure after the pressurizing device, but before the throttle body)
G BARO (atmospheric pressure)
Figure 6 — Turbocharger/supercharger pressure sensor location blow-thru system

Components
A air cleaner
B MAF
D Turbocharger/supercharger
E MAP (manifold pressure closest to the intake valves)
G BARO (atmospheric pressure)
Figure 7 — Turbocharger/supercharger pressure sensor location no throttle body (diesel)
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ISO 15031-6:2005(E)
3.7
left/right and front/rear
component identified by its position as if it can be viewed from the drivers seating position
3.8
“A” “B”
manufacturer defined when components indicated by a letter
3.9
intermittent/erratic
temporarily discontinuous signal where the duration of the fault is not sufficient to be considered open or short,
or the rate of change is excessive
4 General specifications
Table 1 specifies systems, code categories, hexadecimal values and particular sections of electrical/electronic
systems diagnostic.
Table 1 — General code specifications
System Code categories Hex value Appendix
B0xxx – B3xxx 8xxx – Bxxx
Body B
Chassis C0xxx – C3xxx 4xxx – 7xxx C
Powertrain P0xxx – P3xxx 0xxx – 3xxx P
Network U0xxx – U3xxx Cxxx – Fxxx U
The recommended DTCs consist of a three-digit numeric code preceded by an alphanumeric designator. The
alphanumeric designators are “B0”, “B1”, “B2”, “B3”, “C0”, “C1”, “C2”, “C3”, “P0”, “P1”, “P2”, “P3”, “U0”, “U1”,
“U2”, “U3”, corresponding to four sets of body, four sets of chassis, four sets of powertrain and four sets of
network trouble codes. The code structure itself is partially open-ended. A portion of the available numeric
sequences (portions of “B0”, “C0”, “P0”, “P2”, “P3”, “U0” and “U3”) is reserved for uniform codes assigned by
this or future updates. Detailed specifications of the DTC format structure are specified in Clause 5. Most
circuit, component, or system diagnostic trouble codes that do not support a subfault strategy are specified by
four basic categories:
⎯ Circuit/open,
⎯ Range/performance,
⎯ Circuit low, and
⎯ Circuit high.
Circuit low is measured with the external circuit, component, or system connected. The signal type (voltage,
frequency, etc.) shall be included in the message after circuit low or circuit high.
Circuit high is measured with the external circuit, component, or system connected. The signal type (voltage,
frequency, etc.) may be included in the message after circuit low or circuit high.
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ISO 15031-6:2005(E)
5 Format structure
5.1 Description
The diagnostic trouble code consists of an alphanumeric designator, B0-B3 for body, C0-C3 for chassis,
P0-P3 for powertrain, and U0-U3 for network communication, followed by three characters. The assignment of
the proper alpha designator should be determined by the area most appropriate for that function. In most
cases, the alpha designator will be implied since diagnostic information will be requested from a particular
controller. However, this does not imply that all codes supported by a particular controller shall have the same
alphanumeric designator. The codes are structured as in Figure 8.

Figure 8 — Structure of diagnostic trouble codes
EXAMPLE 1 The 2-byte DTC as a data bus value $9234 would be displayed to technicians as the manufacturer
controlled body code B1234 (see Figure 9).
DTC High Byte DTC Low Byte
$9 $2 $3 $4
1 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0
B 1 2 3 4
Figure 9 — Example of 2-byte diagnostic trouble code structure
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ISO 15031-6:2005(E)
EXAMPLE 2 The 3-byte DTC as a data bus value $923400 would be displayed to technicians as the manufacturer
controlled body code B1234-00 (see Figure 10). See Annex D for DTC Low Byte (Failure Type Byte) definitions. The low
byte shall be displayed in hexadecimal format, e.g. $1A shall be displayed as 1A.
DTC High Byte DTC Middle Byte DTC Low Byte
$9 $2 $3 $4 $0 $0
1 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 0 0 0 0 0 0 0 0
B 1 2 3 4 0 0
Figure 10 — Example of 3-byte diagnostic trouble code structure
Codes have been specified to indicate a suspected trouble or problem areas, and are intended to be used as
a directive to the proper service procedure. To minimize service confusion, fault codes should not be used to
indicate the absence of problems or the status of parts of the system (e.g. powertrain system O.K., or MIL
activated), but should be confined to indicate areas in need of service attention.
Ranges have been expanded beyond 100 numbers by using the hexadecimal base 16 number system.
5.2 ISO/SAE controlled codes (core DTCs)
ISO/SAE-controlled diagnostic trouble codes are those codes where industry uniformity has been achieved.
These codes were felt to be common enough across most manufacturers’ applications that a common number
and fault message could be assigned. All unspecified numbers in each grouping are ISO/SAE reserved for
future growth. Although service procedures may differ widely amongst manufacturers, the fault being indicated
is common enough to be assigned a particular fault code. Codes in this area are not to be used by
manufacturers until they have been approved by ISO/SAE.
5.3 Manufacturer controlled codes (non-uniform DTCs)
Areas within each alpha designator have been made available for manufacturer-controlled DTCs. These are
fault codes that will not generally be used by a majority of the manufacturers due to basic system differences,
implementation differences, or diagnostic strategy differences. Each vehicle manufacturer or supplier who
designs and specifies diagnostic algorithms, software and diagnostic trouble codes are strongly encouraged to
remain consistent across their product line when assigning codes in the manufacturer-controlled area. For
powertrain codes, where possible, the same groupings should be used as in the ISO/SAE controlled area,
i.e. 100’s and 200’s for fuel and air metering, 300’s for ignition system or misfire, etc.
While each manufacturer has the ability to define the controlled DTCs to meet its specific controller algorithms,
all DTC words shall meet ISO 15031-2.
5.4 Body system groupings (DTC numbers and descriptions are given in Annex C)
5.4.1 B0XXX ISO/SAE controlled
5.4.2 B1XXX manufacturer controlled
5.4.3 B2XXX manufacturer controlled
5.4.4 B3XXX reserved by document
5.5 Chassis system groupings (DTC numbers and descriptions are given in Annex C)
5.5.1 C0XXX ISO/SAE controlled
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ISO 15031-6:2005(E)
5.5.2 C1XXX manufacturer controlled
5.5.3 C2XXX manufacturer controlled
5.5.4 C3XXX reserved by document
5.6 Powertrain system groupings (DTC numbers and descriptions are given in Annex B)
5.6.1 P0XXX ISO/SAE controlled
5.6.2 P1XXX manufacturer control
5.6.3 P2XXX ISO/SAE controlled
5.6.4 P3XXX manufacturer controlled and ISO/SAE reserved
5.7 Network groupings (DTC numbers and descriptions are given in Annex C)
5.7.1 U0XXX ISO/SAE controlled
5.7.2 U1XXX manufacturer controlled
5.7.3 U2XXX manufacturer controlled
5.7.4 U3XXX manufacturer controlled and ISO/SAE reserved
6 Diagnostic trouble code descriptions
6.1 Diagnostic trouble code application
Recent developments have expanded the scope of this documentation to include additional DTCs and
descriptions for network systems, body systems and chassis systems. Two different DTC application methods
are required depending on the system. Powertrain DTCs require the assignment of a unique DTC number and
description for each failure mode (e.g. circuit low, circuit high, rationality, etc.). Body and chassis systems
descriptions are more general and require the assignment of a single DTC number and description for each
component, not failure mode. Unique body and chassis failure mode identification is still possible, but is
dependent upon using diagnostic protocols that support a subfault failure strategy. One example is
ISO 14229-1, which uses a “Failure Type Byte” associated with each DTC to describe the failure mode (e.g.
circuit low, circuit high, rationality, etc.). However, any protocol supporting a subfault strategy will work with
these DTCs. Manufacturers shall select the appropriate failure mode to apply to the base DTC description.
6.2 Powertrain systems
The powertrain systems category covers functions that include engine, transmission and associated drivetrain
accessories. For powertrain systems, each specified fault code has been assigned a description to indicate
the circuit, component or system area that was determined to be at fault. The descriptions are organized such
that different descriptions related to a particular sensor or system are grouped together. In cases where there
are various fault descriptions for different types of faults, the group also has a “generic” description as the first
code/message of the group. A manufacturer has a choice when implementing diagnostics, based on the
specific strategy and complexity of the diagnostic.
Where more specific fault descriptions for a circuit, component or system exist, manufacturers should choose
the code most applicable to their diagnosable fault. The descriptions are intended to be somewhat general to
allow manufacturers to use them as often as possible yet still not conflict with their specific repair procedures.
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ISO 15031-6:2005(E)
The terms “low” and “high” when used in a description, especially those related to input signals, refer to the
voltage, frequency, etc. at the pin of the controller. The specific level of “low” and “high” shall be specified by
each manufacturer to best meet their needs.
For example, in diagnosing a 5 V reference Throttle Position Sensor (TP Sensor), if the input signal at the
Powertrain Control Module (PCM) is stuck near 0 V, a manufacturer has the flexibility to select from either of
two codes — P0120 (Throttle/Pedal Position Sensor/Switch A Circuit) or P0122 (Throttle/Pedal Position
Sensor/Switch A Circuit Low), depending on the manufacturer’s diagnostic procedures. If the input signal at
the PCM is stuck near 5 V, a manufacturer has the flexibility to select from either of two codes — P0120
(Throttle/Pedal Position Sensor/Switch A Circuit) or P0123 (Throttle/Pedal Position Sensor/Switch A Circuit
High), depending on the manufacturer’s diagnostic procedures. If the input signal at the PCM is stuck at 1,5 V
at idle instead of the expected 1,0 V, the manufacturer has the flexibility to select from either of two codes —
P0120 (Throttle/Pedal Position Sensor/Switch A Circuit) or P0121 (Throttle/Pedal Position Sensor/Switch A
Circuit Range/Performance), depending on the manufacturer’s diagnostic procedures. The root cause of the
higher than expected TP Sensor voltage may be either a faulty TP Sensor, corrosion in the TP Sensor
connections or an improperly adjusted throttle plate. Identification of the root cause is done using the
diagnostic procedures, and is not implied by the DTC message, thus allowing the manufacturer flexibility in
assigning DTCs.
6.3 Body systems
The body systems category covers functions that are, generally, inside of the passenger compartment. These
functions provide the vehicle occupants with assistance, comfort, convenience and safety. Each specified
trouble code has been assigned a description to indicate the component or system area that was determined
to be at fault. Unlike powertrain systems, the body system trouble code descriptions are intended to be
general. Powertrain DTCs typically include separate DTCs for each failure mode (e.g. circuit low, circuit high,
rationality, etc.) within each DTC description. Body system DTCs are designed to only support the base
component in the description, which makes these DTCs dependent upon diagnostic protocols that support a
subfault failure strategy. Manufacturers must select the appropriate failure mode (e.g. circuit short to ground,
circuit short to battery, signal plausibility failure, etc.) to apply to the general DTC description. The supported
body subsection included in this group is Restraints.
6.4 Chassis systems
The chassis systems category covers functions that are, generally, outside of the passenger compartment.
These functions typically include mechanical systems such as brakes, steering and suspension. Each
specified trouble code has been assigned a description to indicate the component or system area that was
determined to be at fault. Unlike powertrain systems, the chassis system trouble code descriptions are
intended to be general. Powertrain DTCs typically include separate DTCs for each failure mode (e.g. circuit
low, circuit high, rationality, etc.) within each DTC description. Chassis system DTCs are designed to only
support the base component in the description, which makes these DTCs dependent upon diagnostic
protocols that support a subfault failure strategy. Manufacturers must select the appropriate failure mode (e.g.
circuit short to ground, circuit short to battery, signal plausibility failure, etc.) to apply to the general DTC
description. The supported chassis subsections included in this group are Brakes and Traction Control.
6.5 Network and vehicle integration systems
The network communication and vehicle integration systems category covers functions that are shared among
computers and/or systems on the vehicle. Each specified trouble code has been assigned a description to
indicate the component or system area that was determined to be at fault. The descriptions of data links are
intended to be general in order to allow manufacturers to use them for different communication protocols. The
descriptions of control modules are intended to be general in order to allow manufacturers to reuse the DTC
for new control modules as technologies evolve. Also, the descriptions may be supplemented with additional
subfault information such as the “Failure Type Byte” data defined in Annex D. The subsections included in this
group are Network Electrical, Network Communication, Network Software, Network Data and Control
Module/Power Distribution.
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ISO 15031-6:2005(E)
7 Change requests
Use this form to pass your request:
Request Form for new ISO 15031-6/SAE J2012 controlled DTC
What is the purpose of the component, circuit, or system?
Example: Exhaust Gas Recirculation.
What is the purpose of the diagnostic?
Example: Detect low EGR flow.
Requested Group Number___________________________________________________________________
Requested DTC Number ____________________________________________________________________
Requested DTC Nomenclature _______________________________________________________________
Example: EGR Low Flow Detected.
Requested by: ____________________________________________________________________________
Phone/Fax ________________________________
Email_____________________________________
Address___________________________________
Date:
Please send completed form(s) to both addresses:
FAKRA SAE Headquarters
Normenausschuß Kraftfahrzeuge 755 West Big Beaver Road
Postfach 17 05 63 Suite 1600
D-60079 Frankfurt/Main Troy, MI 48084
Germany USA
ATTN: ISO/TC22/SC3/WG1 ATTN: J2012 Committee Chairman
Fax: +49-69-97507-209
e-mail: fritzsche@vda.de
© ISO 2005 – All rights reserved
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